This invention relates to a camera module and, in particular, to an autofocus camera module for use in a portable compact camera.
The portable compact camera is mounted in a camera-equipped cellular mobile phone. The portable compact camera is provided with the autofocus camera module. Previously, various autofocus camera modules have been proposed.
By way of illustration, Japanese Unexamined Patent Application Publication No. 2006-258969 (JP-A-2006-258969) (which will be also called a first patent document) discloses a camera-equipped cellular mobile phone which is capable of shortening a time required for automatic focusing. The camera-equipped cellular mobile phone (a camera module) disclosed in the first patent document comprises an actuator (a lens driving device) for movably supporting a lens (a lens assembly, a lens barrel) along the direction of an optical axis of the lens, a sensor board on which an image pickup device and electronic parts are mounted, and a sealing member disposed between the above-mentioned actuator and the sensor board. By combining with the sensor board, the sealing member forms an enclosed space for sealing the image pickup device and the electronic parts. The actuator comprises an actuator body and an actuator base. The sealing member is also referred to as a sensor base. That is, a conventional camera module comprises four members (parts): the actuator body, the actuator base, the sensor base, and the sensor board.
The actuator body disclosed in the first patent document comprises a holder (a lens holder) including a tubular portion having an end to which the lens (the lens assembly, the lens barrel) is mounted, a driving coil fixed to the holder (the lens holder) so as to position around the tubular portion of the holder, a yoke comprising a permanent magnet opposite to the driving coil, a pair of leaf springs disposed to both sides of the tubular portion of the holder (the lens holder) in the direction of the optical axis. The pair of leaf springs supports the holder (the lens holder) in the direction of the optical axis shiftably so as to position the holder (the lens holder) in a radial direction. By energizing the driving coil, it is possible to positionally adjust the lens (the lens assembly) in the direction of the optical axis according to interaction between a magnetic field of the permanent magnet and a magnetic field due to an electric current flowing through the driving coil. In the pair of leaf springs, the one is called an upper leaf spring (a front-side spring), the other is called a lower leaf spring (a rear-side spring). The upper leaf spring (the front-side spring) has an inner end portion which is sandwiched between an upper end (a front end) of the holder and a stopper to be fitted to the holder (the lens holder).
Disclosed in the first patent document, the conventional camera module has problems as follows.
A first problem is that it is difficult to assemble the camera module with high position accuracy. This is because the conventional camera module comprises the four members (parts): the actuator body, the actuator base, the sensor base, and the sensor board.
A second problem is that the camera module has a high cost. This is because, in order to assemble the actuator base with the sensor base, it is necessary to provide with a sing-shaped convex portion and a ring-shaped concave portion preventing the entry of dirt and the entry of light in the manner which will later be described in conjunction with FIGS. 1 and 2. In addition, in order to assemble the actuator base with the sensor base, it is necessary to subject evaporation processing of a shielding film to both of them to shield them in common.
A third problem is that it is difficult to lower a height of the camera module. This is because, inasmuch as the conventional camera module comprises the four members (parts): the actuator body, the actuator base, the sensor base, and the sensor board, the height thereof becomes high due to thicknesses of the respective members (parts).